As a tool for noise characteristic evaluation or immunity evaluation, a probe being able to detect an electric field or a magnetic field in high accuracy and in its 3 components of xyz is desired, and a probe using a laser light and optical material has been developed for these purposes. Such a probe is composed of an optical measurement apparatus like a laser optical source and EO/MO material. The electric/magnetic field is measured based on a basic principle that a laser light enters into the material and the refractive index of the material is changed correspondingly to the intensity of the electric/magnetic field. This kind of apparatus is grossly classified into: a type in which alight emitted from a laser optical source propagates in a space and enters into the EO/MO material; and a type in which whole of an optical measurement apparatus and the EO/MO material is connected by an optical fiber, and a laser light propagates through the optical fiber and enters into the material. Because high spatial resolution measurement in a micro region becomes possible by the microfabrication of the EO/MO material, such a probe is expected to achieve high performance in a performance evaluation, a trouble check, or an electric design for electronic circuits or parts mounted in high density.
Japanese Patent Application Publication JP2007-57324A is an example of the optical fiber type measurement system which optically detects the electric field intensity, magnetic field intensity or the like. A purpose of this technique is to prevent a variation of the detection sensitivity of a polarization maintaining fiber before and after a change of the environmental temperature, the stress magnitude or the like.